"After 25 years, I have decided to leave Dream Theater," says Portnoy. "After
having had such amazing experiences playing with Hail, Transatlantic and Avenged
Sevenfold this past year, I have sadly come to the conclusion that I have
recently had more fun and better personal relations with these other projects
than I have for a while now in Dream Theater." -His Facebook page
The decision came just before the band started to record their new album in Jan. 2011 and before kicking off another world tour. You can read more about it in this article here.